The prospective cardiac neural crest, a cell population that contributes to the great arteries of the heart, resides in the dorsal aspect of the hindbrain at neural tube stages. However, no information is available on the origin and state of commitment of presumptive cardiac crest cells in the epiblast before neural fold formation. This proposal aims to 1) identify the location of prospective cardiac neural crest in the epiblast in chick, 2) determine the state of commitment of this cell population in the epiblast. Preliminary results suggest that, at gastrula stage 4, cardiac neural crest precursors are not yet segregated from other crest along the anterior posterior axis. My next experiments will aim at identifying the cardiac crest precursors between stage 4 and stage 9. Because the cardiac neural crest, unlike other neural crest, is committed to its fate by neural tube stage 9, I hypothesize that the cardiac crest might already be committed before neural tube stage. I will use Dil labeling, electroporation, quail/chick grafts and time-lapse imaging to resolve the aims listed above. This proposal will further our understanding of the formation of cardiac neural crest and pave the way to a molecular characterization of the induction of the cardiac crest.